A High-Efficiency E-Band Power Amplifier With Optimized Output Matching Network in a 28-nm Bulk CMOS

This brief presents an E-band high-efficiency power amplifier (PA) implemented in a 28-nm bulk CMOS technology. The output matching network (OMN) is optimized for high power and high efficiency through a co-optimization technique where the optimum load admittance (Yopt) is derived by incorporating the loss of the OMN with the active device performance. In the mm-wave band, a transformer with a single turn ratio is widely used for OMN but poses a limitation on the maximum achievable conductance (Gout.max) to be seen by the output transistor. Therefore, a shunt capacitor (CL) is employed in this brief to boost <inline-formula> <tex-math notation="LaTeX">${\mathrm{ G}}_{\mathrm{ out.max}}$ </tex-math></inline-formula> up to the value required for reaching Yopt. Finally, the transformer dimension and <inline-formula> <tex-math notation="LaTeX">${\mathrm{ C}}_{\mathrm{ L}}$ </tex-math></inline-formula> are optimized for high efficiency and power through the co-optimization technique. The measurement shows that the PA exhibits more than 13.4 dBm of saturated power from 65 to 80 GHz. A peak power-added efficiency (PAE) of 27% is achieved at 71 GHz, which is the highest PAE among the reported E-band CMOS PAs to the best of authors’ knowledge. The PAE is maintained higher than 20% from 65 to 75 GHz. The PA exhibits a rms EVM of −25.8 dB, average PAE of 8.7%, and average output power of 5.8 dBm with a 3-Gbps 64-QAM signal.